1. Field of the Invention
The present invention relates to a group of compounds classified in the field of organic chemistry as 3-[(alkoxy)-(aryl or heteroaryl)methyl]-1H-indoles which are useful as colorformers in pressure-sensitive carbonless duplicating systems and thermal marking systems; to processes for the preparation thereof and to pressure-sensitive carbonless duplicating systems and thermal marking systems containing the same.
2. Description of the Prior Art
Several classes of organic compounds of widely diverse structural types are known to be useful as color formers for carbonless duplicating systems. Among the most widely recognized classes are the phenothiazines, for example, benzoyl leuco methylene blue; fluorans, for example, 2'-anilino-6'-diethylaminofluoran; phthalides, for example, crystal violet lactone; methine dyes, for example, Michler's hydrol and derivatives thereof and various other types of color formers currently employed in commercially accepted carbonless duplicating systems. Typical of the many such systems taught in the prior art are those described in U.S. Pat. Nos. 2,712,507, 2,800,457 and 3,041,289 which issued July 5, 1955, July 23, 1957 and June 26, 1962, respectively. Many of the color formers in the prior art suffer one or more disadvantages such as low tinctorial strength poor light stability, poor xerographic copiability, low resistance to sublimation, and low solubility in common organic solvents, the latter disadvantage thus requiring the use of specialized and expensive solvents in order to obtain microencapsulated solutions of sufficient concentration for use in pressure-sensitive copying systems.
The following appear to constitute the most relevant prior art relative to the present invention.
U.S. Pat. No. 3,684,510, patented Aug. 15, 1972 discloses indolylmethane derivatives having the formula ##STR1## in which A is aryl or a heterocyclic aromatic group and R.sub.1 and R.sub.2 are hydrogen, alkyl or aralkyl. The compounds are stated to be useful in combination with arylamino compounds and tetrahalomethane compounds in light-sensitive materials for the production of copies from an original.
U.S. Pat. No. 3,958,815 issued May 25, 1976 discloses in most pertinent part a group of compounds stated to be useful as dye precursors in pressure-sensitive recording materials and having the formula ##STR2## wherein inter alia R.sub.1 and R.sub.2 represent (1) an aryl group substituted with an ether group R.sub.6 --O-- in which R.sub.6 represents a hydrocarbon group or (2) a heterocyclic group; R.sub.3 represents a --XH or --X--R.sub.7 group in which X is oxygen or sulfur and R.sub.7 is an organic group, and m and n are O.
French Pat. No. 1,561,663 published Mar. 28, 1969 discloses in most pertinent part a series of compounds having the formula ##STR3## wherein inter alia R.sub.1 and R.sub.2 are independently hydrogen, alkyl or aryl; B is a carbocyclic or heterocyclic ring system, and E is alkoxy. The compounds are stated to be useful as intermediates in the preparation of triphenylmethane dyes.
M. Scholtz, Chem. Ber. 46, 2138-2146 (1913) discloses a group of (phenyl, substituted-phenyl or furyl) (ethoxy or methoxy) (.alpha.-methylindolyl)methanes prepared by reacting an appropriate benzaldehyde or furfural with .alpha.-methylindole and ethanol or methanol in the presence of a base. No utility is disclosed for these compounds.